WO2008145771A1

WO2008145771A1 - Method and tool for producing composite-material structures

Info

Publication number: WO2008145771A1
Application number: PCT/ES2007/070099
Authority: WO
Inventors: Patricia TABARÉS FERNÁNDEZ; Raúl LLAMAS SANDÍN; Sergio Del Campo Sayago
Original assignee: Airbus España, S.L.
Priority date: 2007-05-28
Filing date: 2007-05-28
Publication date: 2008-12-04
Also published as: EP2159038A1; US20090294040A1; EP2159038A4; CA2688541A1; CN101801649A; BRPI0721694A2

Abstract

The invention relates to a method for producing stiffened structures (1) made from composite materials, formed by an exterior covering (2) and a plurality of stiffeners (3) having a closed cross-section defining an interior opening (6), which method comprises the following steps: a) providing a moulding tool (34); b) providing auxiliary male tools (36) having interior cavities (32) reinforced (33) along the length thereof, said tools being covered by membranes (37) suitable for curing; c) providing stiffeners (3); d) arranging the stiffeners (3) in the tool (34) and the auxiliary male tools (36) in the interior openings (6); e) laminating the exterior coating (2); f) curing the stiffened structure (1) at a high temperature and pressure; g) removing the auxiliary male tools (36) after the section (41) thereof has been reduced; h) and separating the cured, stiffened structure (1) from the tool (34). The invention also relates to the auxiliary male tools (36), including the design of the interior cavities (32), the reinforcement (33) thereof and the fact that the section of same can be maintained or reduced with the application of overpressure or underpressure respectively.

Description

PROCEDURE AND TOOL FOR THE MANUFACTURE OF COMPOSITE MATERIAL STRUCTURES

FIELD OF THE INVENTION

The present invention relates to a process for the manufacture of composite structures for aeronautical fuselages as well as the tools used in such a manufacturing process.

BACKGROUND OF THE INVENTION

In the aeronautical industry, weight is a primary aspect, which is why optimized structures made of composite materials, mainly carbon fiber, prevail over metal structures. Automatic carbon fiber wrapping machines represent a great advance with respect to manual operation. These machines have a head that presses on the surface to be coated, so that this surface must be able to react to said force.

Composite structures for aeronautical fuselages are formed by panels that, in turn, comprise a series of stiffeners. Thus, the application of the above aspects to aeronautical fuselages leads to the integration of the panels that make up said fuselages together with their stiffeners in the least number of operations, while optimizing said stiffeners. The use of closed section stiffeners is increasingly common, as these stiffeners allow for more rigid structures by adding a lower weight per stiffener. However, the incorporation of this type of stiffeners complicates the manufacturing process of composite structures, since interior tools are necessary to the stiffeners that allow the curb of the piece and the material curing operation compound, while it is necessary to be able to extract these tools from inside the stiffeners if they are intended to be hollow.

Processes for the manufacture of these structures are known in which a rigid element is introduced inside the stiffener section to react to the curb pressure and the curing pressure of the composite material. However, these processes are expensive, so it would be desirable to have more efficient processes, an objective that is achieved with the present invention.

SUMMARY OF THE INVENTION

In a first aspect, the present invention proposes a process for the manufacture of stiffened structures in composite materials formed by an outer liner and a plurality of stiffeners whose cross section has a broken contour with at least one wing attached to the liner, delimiting said contour a inner vain, characterized in that it comprises the following steps:

- provide a forming tool with an outer surface similar to that of the structure on the side of the stiffeners, including recesses to house the stiffeners;

- provide auxiliary male tools consisting of elements of a material capable of maintaining its section by applying an overpressure inside the cylindrical cavities existing therein and capable of reducing its section by applying a depression in these cavities; these auxiliary males are manufactured with an exterior geometry similar to the internal opening of the stiffeners and covered by membranes suitable for curing composite materials;

- provide the stiffeners in a fresh or cured state; - arrange the stiffeners in the tool recesses, coupling them to their geometry and dispose in their inner openings the auxiliary male tools coupled to their geometry; helping in this step the tools male auxiliary to the curing membrane to be coupled to the internal geometry of each stiffener;

- laminate the outer covering on the surface formed by the tool, the stiffeners and the auxiliary male tools; reacting the forming tool and auxiliary male tools, thanks to the overpressure applied inside the inner cylindrical cavities, against the rolling force;

- cure the stiffened structure under conditions of high temperature and pressure; - extracting the auxiliary male tools, by reducing after curing the section thereof thanks to the depression applied inside the inner cylindrical cavities; and - separating the stiffened cured structure from the tool.

In a second aspect, the present invention provides auxiliary male tools used in the previous process, made of elastomeric and / or flexible materials. These males have cylindrical cavities of circular or slightly elliptical or oval section along their length, these cavities being reinforced internally with materials (fiberglass, nylon, etc.) that prevent the perimeter increase of the section of The cavity when applying an internal overpressure, while being sufficiently flexible so that, when applying a depression, they allow the collapse of these cavities, thus reducing the section of the male, and thus allowing its subsequent extraction from the interior of the stiffeners . If the interior cavities had an elongated section, when applying an internal overpressure, they would deform trying to acquire a more circular section, also deforming the outer section of the male.

An advantage of the present invention is that it facilitates the manufacture of structures in which the section and the area of the stiffeners vary longitudinally, even these stiffeners may present, at one or both ends, dimensions smaller than in an intermediate section, since that Auxiliary male tools can be shaped so as to adapt to it.

Another advantage of the present invention is that the use of machines with pressure taping head is facilitated, since the auxiliary male tools provide a substrate inside the stiffeners to react against the force of the head.

Other features and advantages of the present invention will be apparent from the detailed description that follows of an illustrative embodiment of its object in relation to the accompanying figures.

DESCRIPTION OF THE FIGURES

Figures 1a, 1b and 1c show schematic views of composite structures for aeronautical fuselages formed by a coating and a plurality of stiffeners in the form of, respectively, omega, trapezoid and irregular Z.

Figure 2 schematically shows the steps of the process according to the invention for the manufacture of a composite structure for aeronautical fuselages formed by a coating and a plurality of omega-shaped stiffeners.

Figure 3 schematically shows the step of the process according to the invention for the manufacture of a composite structure for aeronautical fuselages formed by a coating and a plurality of omega-shaped stiffeners by means of which the coating process of the coating is carried out .

Figure 4 schematically shows the section of the tools used in the process according to the invention for the manufacture of a composite structure for aeronautical fuselages.

Figure 5 schematically shows the step of the process according to the invention for the manufacture of a composite structure for aeronautical fuselages formed by a coating and a plurality of omega-shaped stiffeners through which the curing process is carried out.

Figure 6 schematically shows the steps of the process according to the invention for the manufacture of a composite structure for aeronautical fuselages formed by a coating and a plurality of stiffeners in the form of omega by which the structure of the tooling used for its manufacture is separated .

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the process according to the invention for manufacturing stiffened structures 1 in composite materials formed by a coating 2 and a plurality of omega-shaped stiffeners 3 (Ω) with wings 4 attached to the coating 2, and souls 5 and head is described below. 7 separated from him.

The process object of the present invention is also applicable to the manufacture of a stiffened structure 11 formed by a liner 12 and a plurality of stiffeners 13 in the form of a trapeze with wings 14 attached to the liner 12, and souls 15 and head 17 separated from it , as well as the stiffened structure 21 formed by a lining 22 and a plurality of irregular Z-shaped stiffeners 23 with a wing 24 attached to the lining 22, and souls 25 and head 27 separated from it.

The stiffeners 3, 13, 23 have in common that their cross section has a broken contour with at least one wing 4, 14, 24 attached to the lining 2, 12, 22 delimiting said contour an inner opening 6, 16, 26.

Structures 1, 11, 21 may have an open shape or shape of revolution parts, as is the case with parts of an airplane's fuselage.

In the process according to the invention for the manufacture of a composite structure for aeronautical fuselages formed by a coating and a plurality of stiffeners, as shown in Figure

2, are placed on the forming tool 34 which has recesses 35 the stiffeners in the form of omega 3 and on them the auxiliary male tools 36 covered by a membrane 37 suitable for curing composite materials.

Cured or uncured stiffeners 3 can be used. The auxiliary male tools 36 are made of an elastomeric and / or flexible material, for example silicone, rubber, etc., with cylindrical cavities of circular or slightly elliptical or oval section along their length reinforced with a material, fabric or filaments that prevent, to a greater or lesser extent, the increase of the perimeter of the cavity when applying an internal overpressure, but that allows the collapse of these cavities when applying a depression, so that the section of the male is reduced, thus allowing its extraction of the stiffeners 3. These auxiliary males are made with an external geometry similar to the inner span 6 of the stiffener using an appropriate manufacturing technique. When each auxiliary male 36 is inserted in the opening 6 of the stiffener 3, the curing membrane 37 is helped to engage the internal geometry of each stiffener 3.

The stiffeners 3 and the male tools 36 can be arranged in the forming tool 34, having previously coupled them. In Figure 3 it is observed that in a subsequent step the coating 2 is laminated by the head 38 of a wrapping machine on the surface formed by the forming tool 34, the stiffeners 3 and the membrane 37 covering the auxiliary male tools 36 In this step, the forming tool 34 and the auxiliary male tools 36 react the force of the wrapping head 38.

Figure 4 shows the section of the auxiliary male tools 36 made of an elastomeric material 31, which react against the force of the curb head 38 thanks to the overpressure that is applied inside the interior cavities 32 thereof . With the application of pressure in these quasi-inextensible cavities thanks to the reinforcement 33 they contain, we are thus achieving an effect similar to that which would achieve by introducing, by said cavities, rigid bars (of steel, aluminum, etc.) of the same section as the cavities.

A variant of the procedure is the manual realization of the coating of the coating 2. In Figure 5, it is observed that in a subsequent step a curing membrane 39 is placed on the whole of the structure and, optionally, a treadmill 40. After this, it is cured Ia structure in high temperature conditions and pressure in autoclave. During the curing process, the membrane 37 covering the auxiliary male tools 36 communicates the interior of the stiffeners 3 with the atmosphere inside the autoclave, thus keeping the composite material that surrounds it pressed, that is stiffening 3 and the of laminate 2, causing curing.

Once the structure 1 has been cured and cooled, the auxiliary male tools 36 are removed thanks to the reduction in section 41 that occurs when a depression is applied in the inner cylindrical cavities, thus facilitating the separation of the structure 1 from the forming tool 34 and Ia Removal of the auxiliary male tools 36 inside the stiffeners 3, as illustrated in Figure 6 when representing them with a smaller size than the initial one.

In the preferred embodiment just described, those modifications within the scope defined by the following claims can be introduced

Claims

1. Procedure for the manufacture of stiffened structures (1) in composite materials, said structures (1) comprising an outer covering (2) and a plurality of stiffeners (3) whose cross section has an outline that is delimited by an inner opening ( 6), characterized in that it comprises said process comprises the following steps: a) providing a tool (34) with an outer surface similar to that of the structure (1) on the side of the stiffeners (3), including recesses ( 35) to house the stiffeners (3); b) provide auxiliary male tools (36) comprising interior cavities (32), these tools (36) being able to maintain their section during the laminate of the coating (2) when an overpressure is applied inside the cavities (32) ), while the structure of interior cavities (32) must allow them to collapse when applying a depression inside, so that the section (41) of the male tools (36) is reduced, thus allowing their extraction of the stiffeners (3), these male tools (36) being formed with a geometry similar to the inner opening (6) of the stiffeners (3) and being covered by membranes suitable for curing composite materials; c) provide the stiffeners (3) in the fresh or cured state; d) arrange the stiffeners (3) in the recesses (35) of the tool (34), coupling them to their geometry, and arrange the auxiliary male tools (36) in the inner openings (6) of the stiffeners (3) coupled to its geometry; e) laminate the outer covering (2) on the surface formed by the tool (34), the stiffeners (3) and the auxiliary male tools (36), applying at this time the overpressure necessary to maintain its section; f) cure the stiffened structure (1) under conditions of high temperature and pressure; g) extract the auxiliary male tools (36), previously applying the depression necessary to reduce its section (41); h) separate the stiffened structure (1) cured from the tool (34).

2. Method for manufacturing stiffened structures (1) in composite materials according to claim 1, characterized in that the auxiliary male tools (36) comprise elements of an elastomeric material (31).

3. Method for manufacturing stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that the cavities (32) of the auxiliary male tools (36) are reinforced along their length with a material, fabric or filament (33) that prevents the increase of the perimeter of the cavities (32) when applying an internal overpressure, in order to withstand the pressure of the curb head.

4. Process for the manufacture of stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that the cavities (32) of the auxiliary male tools (36) are cylindrical, circular, elliptical or oval.

5. Method for manufacturing stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that the stiffened structure (1) is a piece of revolution.

6. Method for manufacturing stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that the stiffeners (3) are omega-shaped.

7. Procedure for the manufacture of stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that in stage d) the stiffeners (3) are arranged in the recesses (35) of the tool (34) having previously coupled in its inner openings (6) the auxiliary male tools (36).

8. Method for manufacturing stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that step e) is carried out by means of a head (38) of a wrapping machine.

9. Method for manufacturing stiffened structures (1) in composite materials according to any of the preceding claims, characterized in that prior to step f) a treadmill (40) is placed on the lining (2).

10. Useful auxiliary male (36) used in a process for the manufacture of stiffened structures (1) according to any of claims 1-9, characterized in that it is made of an elastomeric compound.

eleven . Useful auxiliary male (36) according to claim 10, characterized in that the elastomeric compound is flexible.

12. Useful auxiliary male (36) according to any of claims 10-

1 1, characterized in that it is made with a silicone based compound.

13. Useful auxiliary male (36) according to any of claims 10-

12, characterized in that it comprises a plurality of cavities (32) along its length.

14. Useful auxiliary male (36) according to any of claims 10-13, characterized in that the cavities (32) are cylindrical (32) of circular, elliptical or oval section.